This invention relates to shaft seals and particularly to such seals having hydrodynamic characteristics.
Many types of shaft seals are known in the prior art and many such seals include ribs or ridges angularly displaced so as to provide a pumping action to return errant fluid, which may have passed the seal because of imperfections in the shaft, to the fluid side of the seal. Most such prior art devices have a resilient sealing portion which is formed by molding. Molding is a comparatively expensive operation and not well suited to certain otherwise desirable materials paticularly polytetrafluoroethylene.
It has also been proposed to form hydrodynamic shaft seals utilizing a plurality of differently formed "washers" of materials such as polytetrafluoroethylene, the washers being stacked axially along the shaft and each of the washers performing a separate function to provide an overall seal. An example of such a seal is found in U.S. Pat. No. 3,801,114. While being somewhat more amenable to construction with materials such as polytetrafluoroethylene than the prior art molded seals such a seal is nevertheless relatively complicated.
It is an object of the present invention to provide a seal which can be readily made from materials such as polytetrafluoroethylene.
It is another object of this invention to provide such a seal which utilizes a minimum number of parts and is therefore simple and inexpensive to manufacture.
It is a further object of this invention to provide such a seal having excellent hydrodynamic pumping characteristics.